1. Field of the Invention
The present invention relates to a navigation system for a movable body such as an on-vehicle navigation system or the like, a navigation method for a movable body, a program storage device and a computer data signal embodiment in a carrier wave, especially to those which are preferably used for an electronically controlled or computerized movable body having an apparatus for detecting biological information or an ACC (Adaptive Cruise Control) apparatus and so on.
2. Description of the Related Art
Nowadays, research and development on electronic control for controlling a drive of a vehicle are advanced, and a navigation system for aiding in driving is significantly spread and popularized.
As an example of this electronic control of a drive of a vehicle, there is what is referred to as the ACC. This is intended to detect a leading vehicle (i.e., another vehicle moving ahead of a self-vehicle) by millimeter wave radar, control an accelerator and a brake, hold a vehicle speed and a following distance or a distance between two vehicles, and decelerate or stop automatically depending on the behavior of the leading vehicle on a crowded road. There is also another type of ACC, which may have such a function that generates an alert sound or display a warning in the case that the following distance becomes shorter than a predetermined distance. Namely, the ACC function judges a driving condition of the leading vehicle and allows an automatic drive regarding the vehicle speed and the following distance, so that it can relieve a driver's driving burden. Moreover, the ACC function makes it possible to drive in a comfortable driving condition set by a driver in the case that there is no leading car.
The navigation system for aiding in driving is designed to display map data, current position data, data of route to a destination, various types of guidance data, and the like on a display device or to output as voice or sound a warning message, a guidance message, or the like for navigation by a speaker mounted on the vehicle. The current position data are obtained by a GPS (Global Positioning System) apparatus, or by a self-contained or built-in positioning apparatus such as an angular velocity sensor, an acceleration sensor, a velocity sensor or the like (i.e. various types of measurement apparatuses for a traditional SCN (Self-Contained Navigation)) to obtain position information, either or both of which are mounted on a vehicle. Moreover, a communication navigation system, on which some development are now making progress, is equipped with a wireless communication device and is designed to aid in driving by exchanging radio messages with an outer information source and by catching objective information to display it or to output it as voice or sound.
However, the behavior of a vehicle that is automatically controlled is sometimes different from a driving condition that a driver expects. For example, in the case of following a low-speed leading vehicle on a blind road that gives a poor visibility such as a mountain path or the like, even if the following distance is held by the ACC, the uncertainty of when a driver can overtake the leading car gives him or her mental stress.
Moreover, in the case of encountering traffic congestion or jams, a driver usually receives stress mentally and/or physically. In this case, the driver desires to escape from the traffic congestion; however, there is hardly any device for aiding or helping the driver's desire, i.e. there is hardly any system that judges a surrounding condition and automatically presents information on overtakability such as whether or not it is overtakable (i.e., whether or not the self-vehicle is able to “overtake” the leading vehicle); if there is an overtakable point, where it is; how long it will take to reach the point; and so on.
As described above, according to an existing ACC and navigation system, there is such a problem that in the case a driver is feeling stressed to a low-speed leading vehicle or the like, it is difficult to present information indicating it is safely overtakable, even if a vehicle can do that in view of an actual road condition or road rules etc.